Control circuit, light source driving device and display apparatus

ABSTRACT

The present disclosure provides a control circuit, a light source driving device and a display apparatus. The control circuit comprises a current source circuit configured to generate a current signal having a magnitude positively correlated with a temperature of a region where the control circuit is located; a conversion circuit coupled to the current source circuit and configured to convert the current signal generated by the current source circuit into a voltage signal; and a first comparison circuit coupled to the conversion circuit and configured to output a control signal for controlling brightness of a light source according to the voltage signal received from the conversion circuit, a magnitude of the control signal being negatively correlated with the temperature of the region where the control circuit is located, and the brightness of the light source being positively correlated with the magnitude of the control signal.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese Patent Application No.201810155293.9, filed on Feb. 23, 2018, the contents of which areincorporated by reference in the entirety.

TECHNICAL FIELD

The present disclosure relates to the field of display technology, moreparticularly, to a control circuit, a light source driving device and adisplay apparatus.

BACKGROUND

In a liquid crystal display apparatus, a driving circuit and a backlightsource may generate a large amount of heat during operation, resultingin increased temperature of the liquid crystal display apparatus. Whenthe temperature is high enough to reach a certain high level, a liquidcrystal display panel or the driving circuit may operate abnormally oreven be burned.

SUMMARY

In an aspect, the present disclosure provides a control circuitincluding:

a current source circuit configured to generate a current signal havinga magnitude positively correlated with a temperature of a region wherethe control circuit is located;

a conversion circuit coupled to the current source circuit andconfigured to convert the current signal generated by the current sourcecircuit into a voltage signal; and

a first comparison circuit coupled to the conversion circuit andconfigured to output a control signal for controlling brightness of alight source according to the voltage signal received from theconversion circuit, a magnitude of the control signal being negativelycorrelated with the temperature of the region where the control circuitis located, and the brightness of the light source being positivelycorrelated with the magnitude of the control signal.

In an embodiment, the first comparison circuit includes a first inputterminal and a second input terminal, and at least one of the firstinput terminal and the second input terminal is coupled to theconversion circuit and configured to receive the voltage signal from theconversion circuit, and

the first comparison circuit is configured to output the control signalin response to a magnitude of a voltage signal input to the first inputterminal being greater than a magnitude of a voltage signal input to thesecond input terminal, the magnitude of the control signal beingnegatively correlated with a different between the voltage signals inputto the first input terminal and the second input terminal of the firstcomparison circuit.

In an embodiment, the conversion circuit includes a first conversionsub-circuit coupled to the first input terminal of the first comparisoncircuit and configured to provide a first voltage signal to the firstinput terminal of the first comparison circuit, a magnitude of the firstvoltage signal being positively correlated with a magnitude of thecurrent signal generated by the current source circuit.

In an embodiment, the conversion circuit includes a second conversionsub-circuit coupled to the second input terminal of the first comparisoncircuit and configured to provide a second voltage signal to the secondinput terminal of the first comparison circuit, a magnitude of thesecond voltage signal being negatively correlated with the magnitude ofthe current signal generated by the current source circuit.

In an embodiment, the control circuit further includes a secondcomparison circuit configured to output a turn-off signal forcontrolling a display apparatus having the control circuit to be turnedoff in response to a magnitude of a voltage signal input to a firstinput terminal thereof being greater than a magnitude of a voltagesignal input to a second input terminal thereof, and

the first conversion sub-circuit is further coupled to the first inputterminal of the second comparison circuit, and is configured to generatea third voltage signal having a magnitude positively correlated with themagnitude of the current signal generated by the current source circuitand output the third voltage signal to the first input terminal of thesecond comparison circuit; the magnitude of the third voltage signalsmaller lower than the magnitude of the first voltage signal.

In an embodiment, the second conversion sub-circuit is further coupledto the second input terminal of the second comparison circuit andconfigured to output the second voltage signal to the second inputterminal of the second comparison circuit.

In an embodiment, the current source circuit includes a currentgeneration circuit configured to generate a bias current signal having amagnitude positively correlated with the temperature of the region wherethe control circuit is located;

the current source circuit further includes a first replica circuitcoupled to the current generation circuit and the first conversionsub-circuit, and configured to supply a first mirror current signalhaving a same magnitude as the magnitude of the bias current signal andoutput the first mirror current signal to the first conversionsub-circuit; and

the first conversion sub-circuit is configured to convert the firstmirror current signal into the first voltage signal.

In an embodiment, the current source circuit further includes a secondreplica circuit coupled to the current generation circuit and the secondconversion sub-circuit, and configured to supply a second mirror currentsignal having a same magnitude as the magnitude of the bias currentsignal and output the second mirror current signal to the secondconversion sub-circuit; and

the second conversion sub-circuit is configured to convert the secondmirror current signal into the second voltage signal.

In an embodiment, the current generation circuit includes a firsttriode, a second triode, a first resistor, a second resistor, a thirdresistor, a first P-type field effect transistor, a second P-type fieldeffect transistor, a third P-type field effect transistor, a fourthP-type field effect transistor, a first N-type field effect transistor,a second N-type field effect transistor, a third N-type field effecttransistor, and a fourth N-type field effect transistor; whereinwidth-to-length ratios of the first to fourth N-type field effecttransistors are the same, and width-to-length ratios of the first tofourth P-type field effect transistors are the same,

a gate electrode of the first P-type field effect transistor is coupledto a second electrode of the second P-type field effect transistor, afirst electrode of the first P-type field effect transistor is coupledto a power supply terminal, and a second electrode of the first P-typefield effect transistor is coupled to a first electrode of the secondP-type field effect transistor;

a gate electrode of the third P-type field effect transistor is coupledto the gate electrode of the first P-type field effect transistor, afirst electrode of the third P-type field effect transistor is coupledto the power supply terminal, and a second electrode of the third P-typefield effect transistor is coupled to a first electrode of the fourthP-type field effect transistor:

a gate electrode of the fourth P-type field effect transistor is coupledto a gate electrode of the second P-type field effect transistor and afirst electrode of the third N-type field effect transistor, and asecond electrode of the fourth P-type field effect transistor is coupledto a gate electrode of the third N-type field effect transistor and agate electrode of the fourth N-type field effect transistor;

a gate electrode of the first N-type field effect transistor is coupledto a gate electrode of the second N-type field effect transistor and afirst electrode of the fourth N-type field effect transistor, and afirst electrode of the first N-type field effect transistor is coupledto a second electrode of the third N-type field effect transistor;

a first electrode of the second N-type field effect transistor iscoupled to a second electrode of the fourth N-type field effecttransistor;

a first terminal of the first resistor is coupled to a second electrodeof the first N-type field effect transistor, a second terminal of thefirst resistor is coupled to an emitter of the first triode, an emitterof the second triode is coupled to a second electrode of the secondN-type field effect transistor, and a base and a collector of the firsttriode and a base and a collector of the second triode are all coupledto a low level signal terminal;

a first terminal of the second resistor is coupled to the secondelectrode of the second P-type field effect transistor, and a secondterminal of the second resistor is coupled to the first electrode of thethird N-type field effect transistor; and

a first terminal of the third resistor is coupled to the secondelectrode of the fourth P-type field effect transistor, and a secondterminal of the third resistor is coupled to the first electrode of thefourth N-type field effect transistor.

In an embodiment, the first replica circuit includes a fifth P-typefield effect transistor, a gate electrode of the fifth P-type fieldeffect transistor is coupled to the gate electrode of the first P-typefield effect transistor, a first electrode of the fifth P-type fieldeffect transistor is coupled to the power supply terminal, and a secondelectrode of the fifth P-type field effect transistor is coupled to thefirst conversion sub-circuit; and a width-to-length ratio of the fifthP-type field effect transistor is equal to the width-to-length ratio ofthe first P-type field effect transistor.

In an embodiment, the second replica circuit includes a sixth P-typefield effect transistor, a gate electrode of the sixth P-type fieldeffect transistor is coupled to the gate electrode of the first P-typefield effect transistor, a first electrode of the sixth P-type fieldeffect transistor is coupled to the power supply terminal, and a secondelectrode of the sixth P-type field effect transistor is coupled to thesecond conversion sub-circuit; and a width-to-length ratio of the sixthP-type field effect transistor is equal to the width-to-length ratio ofthe first P-type field effect transistor.

In an embodiment, the first comparison circuit includes:

a transconductance amplifier having a non-inverting input terminalcoupled to the first input terminal of the first comparison circuit, aninverting input terminal coupled to the second input terminal of thefirst comparison circuit and an output terminal coupled to an outputterminal of the first comparison circuit; a positive power supplyterminal of the transconductance amplifier is coupled to the currentsource circuit, and a negative power supply terminal of thetransconductance amplifier is coupled to the low level signal terminal;

a sixth resistor having a first terminal coupled to the output terminalof the first comparison circuit and a second terminal coupled to the lowlevel signal terminal; and

a seventh resistor having a first terminal coupled to the power supplyterminal, and a second terminal coupled to the output terminal of thefirst comparison circuit.

In an embodiment, the current source circuit further includes a seventhP-type field effect transistor, a gate electrode of the seventh P-typefield effect transistor is coupled to the gate electrode of the firstP-type field effect transistor, a first electrode of the seventh P-typefield effect transistor is coupled to the power supply terminal, and asecond electrode of the seventh P-type field effect transistor iscoupled to the positive power supply terminal of the transconductanceamplifier.

In an embodiment, the first conversion sub-circuit includes a resistorbranch, the resistor branch includes at least one resistor, a firstterminal of the resistor branch is coupled to the second electrode ofthe fifth P-type field effect transistor, a second terminal of theresistor branch is coupled to the low level signal terminal, and thefirst input terminal of the first comparison circuit is coupled to thefirst terminal of the resistor branch.

In an embodiment, the second conversion sub-circuit includes a thirdtriode, a base and a collector of the third triode are coupled to thelow level signal terminal, and an emitter of the third triode is coupledto the second input terminal of the first comparison circuit and thesecond electrode of the sixth P-type field effect transistor.

In an embodiment, the first conversion sub-circuit includes a fourthresistor and a fifth resistor, a first terminal of the fourth resistoris coupled to a first terminal of the fifth resistor, a second terminalof the fourth resistor is coupled to the low level signal terminal, anda second terminal of the fifth resistor is coupled to the secondelectrode of the fifth P-type field effect transistor; the first inputterminal of the second comparison circuit is coupled to the firstterminal of the fourth resistor, and the second input terminal of thesecond comparison circuit is coupled to the emitter of the third triode.

In an embodiment, the second comparison circuit includes a voltagecomparator, a non-inverting input terminal of the voltage comparator iscoupled to the first input terminal of the second comparison circuit, aninverting input terminal of the voltage comparator is coupled to thesecond input terminal of the second comparison circuit, and an outputterminal of the voltage comparator is coupled to the output terminal ofthe second comparison circuit.

In an embodiment, the current source circuit further includes an eighthP-type field effect transistor, a gate electrode of the eighth P-typefield effect transistor is coupled to the gate electrode of the firstP-type field effect transistor, a first electrode of the eighth P-typefield effect transistor is coupled to the power supply terminal, asecond electrode of the eighth P-type field effect transistor is coupledto a positive power supply terminal of the voltage comparator, and anegative power supply terminal of the voltage comparator is coupled tothe low level signal terminal.

Correspondingly, the present disclosure further provides a light sourcedriving device including the above control circuit and a light sourcedriving circuit coupled to the control circuit, wherein the light sourcedriving circuit is configured to adjust brightness of a light sourceaccording to the control signal output by the control circuit such thatthe adjusted brightness of the light source is positively correlatedwith the magnitude of the control signal.

In an embodiment, the light source driving circuit includes:

a pulse generator coupled to the control circuit and configured togenerate a pulse modulation signal according to the control signaloutput by the control circuit, a duty cycle of the pulse modulationsignal being positively correlated with the magnitude of the controlsignal;

a power source configured to provide a current to a light-emittingelement of the light source:

a switch element coupled to the pulse generator, the power source, andthe light-emitting element, and configured to control connection anddisconnection between the power source and the light-emitting elementaccording to the pulse modulation signal from the pulse generator tocontrol an average current of the light-emitting element.

Correspondingly, the present disclosure further provides a displayapparatus including a display module and the above light source drivingdevice, the display module includes a backlight coupled to the lightsource driving device, and the light source driving device is configuredto adjust brightness of the backlight.

In an embodiment, the display apparatus further includes a gatingswitch, the control circuit includes a second comparison circuit, thesecond comparison circuit is configured to output a turn off signal forcontrolling the display apparatus to be turned off according to thevoltage signal received from the conversion circuit, the gating switchis coupled between the display module and a power supply terminal forsupplying power to the display module, a control terminal of the gatingswitch is coupled to the second comparison circuit of the controlcircuit, and the gating switch is configured to disconnect the powersupply terminal from the display module upon receipt of the turn-offsignal from the second comparison circuit of the control circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings, which constitute part of the specification, are intendedto provide a further understanding of the present disclosure, andexplain the present disclosure together with specific implementations,rather than limiting the present disclosure. In the drawings:

FIG. 1 is a block diagram of a control circuit according to anembodiment of the present disclosure;

FIG. 2 is a schematic structural diagram of a control circuit accordingto an embodiment of the present disclosure;

FIG. 3 is a schematic structural diagram of a light source drivingcircuit of a light source driving device according to an embodiment ofthe present disclosure;

FIG. 4 is a schematic diagram illustrating principle of obtaining apulse modulation signal from a sawtooth wave signal V1 and a controlsignal according to an embodiment of the present disclosure; and

FIG. 5 is a schematic diagram illustrating principle of controlling adisplay module to be turned off according to an embodiment of thepresent disclosure.

DETAILED DESCRIPTION

The specific implementations of the present disclosure will be describedin detail below with reference to the accompanying drawings. It is to beunderstood that the specific implementations described herein are merelyused for describing and explaining the present disclosure, and are notintended to limit the present disclosure.

As an aspect of the present disclosure, a control circuit is provided.As shown in FIG. 1, the control circuit includes a current sourcecircuit 10, a conversion circuit 20, and a first comparison circuit 30.The current source circuit 10 is configured to generate a current signalwhose magnitude is positively correlated with a temperature of a regionin which the control circuit is located. The conversion circuit 20 iscoupled to the current source circuit 10 and is configured to convertthe current signal generated by the current source circuit 10 into avoltage signal. The first comparison circuit 30 is coupled to theconversion circuit 20 and configured to output a control signal forcontrolling brightness of a light source according to the voltage signalreceived from the conversion circuit 20. A magnitude of the controlsignal is negatively correlated with the temperature of the region inwhich the control circuit is located, and the brightness of the lightsource is positively correlated with the magnitude of the controlsignal.

In some embodiments, the current source circuit 10 is coupled to a powersupply terminal VDD.

In some embodiments, the first comparison circuit 30 includes a firstinput terminal and a second input terminal, and at least one of thefirst input terminal and the second input terminal is coupled to theconversion circuit 20 and configured to receive the voltage signal fromthe conversion circuit 20.

In some embodiments, the conversion circuit 20 includes a firstconversion sub-circuit 21 and/or a second conversion sub-circuit 22. Thefirst conversion sub-circuit 21 is coupled to the first input terminalof the first comparison circuit 30, and configured to provide a firstvoltage signal to the first input terminal of the first comparisoncircuit 30, and a magnitude of the first voltage signal is positivelycorrelated with a magnitude of the current signal generated by thecurrent source circuit 10. The second conversion sub-circuit 22 iscoupled to the second input terminal of the first comparison circuit 30and configured to provide a second voltage signal to the second inputterminal of the first comparison circuit 30, and a magnitude of thesecond voltage signal is negatively correlated with the magnitude of thecurrent signal generated by the current source circuit 10.

In some embodiments, the first comparison circuit 30 is configured tooutput a control signal, which, for example, may be a voltage signalV_(PWM), when a voltage signal input to its first input terminal ishigher than a voltage signal input to its second input terminal. Themagnitude of the control signal V_(PWM) is negatively correlated with adifference between the voltage signals of the first input terminal andthe second input terminal of the first comparison circuit 30. In anembodiment, the control signal V_(PWM), is used for controllingbrightness of a light source such that the brightness of the lightsource is positively correlated with the magnitude of the control signalV_(PWM).

In an embodiment, the light source is a backlight in a display apparatusIt should be noted that in a case where the conversion circuit 20includes the first conversion sub-circuit 21 but excludes the secondconversion sub-circuit 22, the second input terminal of the firstcomparison circuit 30 may be coupled to a first reference voltageterminal for providing a first reference voltage; in a case where theconversion circuit 20 includes the second conversion sub-circuit 22 butexcludes the first conversion sub-circuit 21, the first input terminalof the first comparison circuit 30 may be coupled to a second referencevoltage terminal for providing a second reference voltage. Magnitudes ofthe first reference voltage and the second reference voltage may be setas practically required such that the voltage signal of the second inputterminal of the first comparison circuit 30 is greater than the voltagesignal of the first input terminal of the first comparison circuit 30when the temperature of the region where the control circuit is locatedis within a normal range (e.g., lower than 60° C.).

The control circuit in the present disclosure may be applied in adisplay apparatus having a backlight. When the temperature of the regionwhere the control circuit is located increases, the current generated bythe current source circuit 10 increases, and at this time, the voltagesignal provided to the first input terminal of the first comparisoncircuit 30 increases (and/or the voltage signal of the second inputterminal of the first comparison circuit 30 decreases), so that thecontrol signal output by the first comparison circuit 30 decreases,which can in turn reduce the brightness of the backlight to reduce thetemperature of the display apparatus.

In some embodiments, as shown in FIG. 2, the current source circuit 10includes a current generation circuit 11, and in a case where theconversion circuit 20 includes the first conversion sub-circuit 21, thecurrent source circuit 10 further includes a first replica circuit 12.In a case where the conversion circuit 20 includes the second conversionsub-circuit 22, the current source circuit 10 further includes a secondreplica circuit 13. In an embodiment, the current generation circuit 11is coupled between the power supply terminal VDD and a low level signalterminal VSS and configured to generate a bias current signal having amagnitude positively correlated with the temperature of the region inwhich the control circuit is located. The first replica circuit 12 iscoupled to the current generation circuit 11 and the first conversionsub-circuit 21, and is configured to replicate the bias current signalto generate a first mirror current signal I_(BIAS1) whose magnitude isequal to the magnitude of the bias current signal, and output the firstmirror current signal to the first conversion sub-circuit 21; the firstconversion sub-circuit 21 is configured to convert the first mirrorcurrent signal into the first voltage signal. The second replica circuit13 is coupled to the current generation circuit 11 and the secondconversion sub-circuit 22, and configured to replicate the bias currentsignal to generate a second mirror current signal I_(BIAS2) whosemagnitude is equal to the magnitude of the bias current signal, andoutput the second mirror current signal to the second conversionsub-circuit 22; the second conversion sub-circuit 22 is configured toconvert the second mirror current signal into the second voltage signal.With current replication by the first replica circuit 12 and the secondreplica circuit 13, the first conversion sub-circuit 21 and the secondconversion sub-circuit 22 can accurately receive the current signalpositively correlated with the temperature.

The control circuit of the present disclosure will be described indetail below with reference to FIGS. 1 and 2. In the following example,the conversion circuit 20 includes both the first conversion sub-circuit21 and the second conversion sub-circuit 22, and the current sourcecircuit 10 includes the current generation circuit 11, the first replicacircuit 12, and the second replica circuit 13.

In some embodiments, the current generation circuit 11 may be a Wilsoncurrent mirror, which includes a first triode Q1, a second triode Q2, afirst resistor R1, a first P-type field effect transistor PM1, a secondP-type field effect transistor PM2, a third P-type field effecttransistor PM3, a fourth P-type field effect transistor PM4, a firstN-type field effect transistor NM1, a second N-type field effecttransistor NM2, a third N-type field effect transistor NM3, and a fourthN-type field effect transistor NM4. The first P-type field effecttransistor PM1, the second P-type field effect transistor PM2, the thirdP-type field effect transistor PM3, and the fourth P-type field effecttransistor PM4 have a same width-to-length ratio, and the first N-typefield effect transistor NM1, the second N-type field effect transistorNM2, the third N-type field effect transistor NM3, and the fourth N-typefield effect transistor NM4 have a same width-to-length ratio.

A gate electrode of the first P-type field effect transistor PM1 iscoupled to a second electrode of the second P-type field effecttransistor PM2, a first electrode of the first P-type field effecttransistor PM1 is coupled to the power supply terminal VDD, and a secondelectrode of the first P-type field effect transistor PM1 is coupled toa first electrode of the second P-type field effect transistor PM2.

A gate electrode of the third P-type field effect transistor PM3 iscoupled to the gate electrode of the first P-type field effecttransistor PM1, a first electrode of the third P-type field effecttransistor PM3 is coupled to the power supply terminal VDD, and a secondelectrode of the third P-type field effect transistor PM3 is coupled toa first electrode of the fourth P-type field effect transistor PM4.

A gate electrode of the fourth P-type field effect transistor PM4 iscoupled to a gate electrode of the second P-type field effect transistorPM2 and a first electrode of the third N-type field effect transistorNM3, and a second electrode of the fourth P-type field effect transistorPM4 is coupled to a gate electrode of the third N-type field effecttransistor NM3 and a gate electrode of the fourth N-type field effecttransistor NM4.

A gate electrode of the first N-type field effect transistor NM1 iscoupled to a gate electrode of the second N-type field effect transistorNM2 and a first electrode of the fourth N-type field effect transistorNM4, and a first electrode of the first N-type field effect transistorNM1 is coupled to a second electrode of the third N-type field effecttransistor NM3.

A first electrode of the second N-type field effect transistor NM2 iscoupled to a second electrode of the fourth N-type field effecttransistor NM4. It could be understood that the P-type field effecttransistors and the N-type field effect transistors each operate in asaturation state.

Two terminals of the first resistor R1 are coupled to a second electrodeof the first N-type field effect transistor NM1 and an emitter of thefirst triode Q1, respectively, and an emitter of the second triode Q2 iscoupled to a second electrode of the second N-type field effecttransistor NM2, and a base and a collector of the first triode Q1 and abase and a collector of the second triode Q2 are all coupled to the lowlevel signal terminal VSS.

In the current generation circuit 11, the width-to-length ratios of thefour P-type field effect transistors are the same, the width-to-lengthratios of the four N-type field effect transistors are the same, thegate electrode of the first P-type field effect transistor PM1 iscoupled to the gate electrode of the third P-type field effecttransistor PM3, the gate electrode of the second P-type field effecttransistor PM2 is coupled to the gate electrode of the fourth P-typefield effect transistor PM4, the gate electrode of the first N-typefield effect transistor NM1 is coupled to the gate electrode of thesecond N-type field effect transistor NM2, and the gate electrode of thethird N-type field effect transistor NM3 is coupled to the gateelectrode of the fourth N-type field effect transistor NM4. Therefore,currents respectively flowing through the first triode Q1 and the secondtriode Q2 have an equal magnitude, and a potential of the secondelectrode of the first N-type field effect transistor NM1 is equal to apotential of the second electrode of the second N-type field effecttransistor NM2. Thus, the magnitude of the bias current signal I_(BIAS)(i.e., the magnitude of the currents respectively flowing through thefirst triode Q1 and the second triode Q2) generated by the currentgeneration circuit 11 is:

$I_{BIAS} = {\frac{V_{{BE}\; 2} - V_{{BE}\; 1}}{R_{1}} = \frac{V_{T} - {\ln\; n}}{R_{1}}}$

where V_(T) is a thermoelectric potential, which is positivelycorrelated with an absolute temperature; R1 is a resistance of the firstresistor R1; n=A₂/A₁, A₁ is a junction area of the first triode Q1, andA2 is a junction area of the second triode Q2; V_(BE1) and V_(BE2) arebase-emitter voltages of the first triode Q1 and the second triode Q2,respectively. It can be seen that the bias current signal is positivelycorrelated with the temperature, and a desired proportional coefficientcan be obtained by appropriately selecting a value of the resistance ofthe first resistor R1.

Further, as shown in FIG. 2, the current generation circuit 11 furtherincludes a second resistor R2 and a third resistor R3. Two terminals ofthe second resistor R2 are coupled to the second electrode of the secondP-type field effect transistor PM2 and the first electrode of the thirdN-type field effect transistor NM3, respectively. Two terminals of thethird resistor R3 are coupled to the second electrode of the fourthP-type field effect transistor PM4 and the first electrode of the fourthN-type field effect transistor NM4, respectively, so that potentials ofthe second terminals of the second and third resistors R2 and R3 changeas potentials of the first terminals of the second and third resistorsR2 and R3 change due to external interference, so as to ensure that afirst terminal of the first resistor R1 and the emitter of the secondtriode Q2 maintain a same potential, thereby increasing the sensitivityof the current generation circuit 11.

In some embodiments, as shown in FIG. 2, the first replica circuit 12may include a fifth P-type field effect transistor PM5. A gate electrodeof the fifth P-type field effect transistor PM5 is coupled to the gateelectrode of the first P-type field effect transistor PM1, a firstelectrode of the fifth P-type field effect transistor PM5 is coupled tothe power supply terminal VDD, and a second electrode of the fifthP-type field effect transistor PM5 is coupled to the first conversionsub-circuit 21. A width-to-length ratio of the fifth P-type field effecttransistor PM5 is the same as the width-to-length ratio of the firstP-type field effect transistor PM1, so that the fifth P-type fieldeffect transistor PM5 and the first P-type field effect transistor PM1form a current mirror. Thereby, the fifth P-type field effect transistorPM5 supplies the first conversion sub-circuit 21 with a current signalhaving the same magnitude as the bias current signal, i.e., a firstmirror current signal I_(BIAS1).

In some embodiments, as shown in FIG. 2, the second replica circuit 13includes a sixth P-type field effect transistor PM6. A gate electrode ofthe sixth P-type field effect transistor PM6 is coupled to the gateelectrode of the first P-type field effect transistor PM1, a firstelectrode of the sixth P-type field effect transistor PM6 is coupled tothe power supply terminal VDD, and a second electrode of the sixthP-type field effect transistor PM6 is coupled to the second conversionsub-circuit 22. A width-to-length ratio of the sixth P-type field effecttransistor PM6 is the same as the width-to-length ratio of the firstP-type field effect transistor PM1, so that the sixth P-type fieldeffect transistor PM6 and the first P-type field effect transistor PM1form a current mirror. Thereby, the sixth P-type field effect transistorPM6 supplies the second conversion sub-circuit 22 with a current signalhaving the same magnitude as the bias current signal, i.e., a secondmirror current signal I_(BIAS2).

In some embodiments, as shown in FIG. 2, the first comparison circuit 30includes a transconductance amplifier OTA, a sixth resistor R6, and aseventh resistor R7. A non-inverting input terminal of thetransconductance amplifier OTA is coupled to the first input terminal ofthe first comparison circuit 30, an inverting input terminal of thetransconductance amplifier OTA is coupled to the second input terminalof the first comparison circuit 30, and an output terminal of thetransconductance amplifier OTA is coupled to the output terminal of thefirst comparison circuit 30. A positive power supply terminal of thetransconductance amplifier OTA is coupled to the current source circuit10, and a negative supply terminal of the transconductance amplifier OTAis coupled to a low level signal terminal. Two terminals of the sixthresistor R6 are coupled to the output terminal of the first comparisoncircuit 30 and the low level signal terminal VSS, respectively. Twoterminals of the seventh resistor R7 are coupled to the power supplyterminal VDD and the output terminal of the first comparison circuit 30,respectively.

In order to provide an operating current to the transconductanceamplifier OTA, as shown in FIG. 2, the current source circuit 10 furtherincludes a seventh P-type field effect transistor PM7, a gate electrodeof the seventh P-type field effect transistor PM7 is coupled to the gateelectrode of the first P-type field effect transistor PM1, a firstelectrode of the seventh P-type field effect transistor PM7 is coupledto the power supply terminal VDD, and a second electrode of the seventhP-type field effect transistor PM7 is coupled to the positive powersupply terminal of the transconductance amplifier OTA. The negativepower supply terminal of the transconductance amplifier OTA is coupledto the low level signal terminal VSS.

When a voltage of the non-inverting input terminal of thetransconductance amplifier OTA is lower than a voltage of the invertinginput terminal of the transconductance amplifier OTA, thetransconductance amplifier OTA does not generate a current, that is,I_(th)=0, and the sixth resistor R6 and the seventh resistor R7 areconnected in series between the power supply terminal VDD and the lowlevel signal terminal VSS, so that there is an initial current in abranch where the sixth resistor R6 and the seventh resistor R7 arelocated. When the voltage at the non-inverting input terminal of thetransconductance amplifier OTA is higher than the voltage of theinverting input terminal of the transconductance amplifier OTA, acurrent I_(th) is input to the output terminal of the transconductanceamplifier OTA (as shown in FIG. 2). As the difference between thevoltages of the non-inverting input terminal and the inverting inputterminal increases, the current I_(th) flowing into the output terminalof the transconductance amplifier OTA increases, the current flowingthrough the sixth resistor R6 decreases, and the voltage across thesixth resistor R6 decreases, so that the voltage signal V_(PWM) outputby the first comparison circuit 30 is lowered.

In some embodiments, the first conversion sub-circuit 21 includes aresistor branch including one resistor or a plurality of resistorsconnected in series. A first terminal of the resistor branch is coupledto the current source circuit 10, a second terminal of the resistorbranch is coupled to the low level signal terminal, and the first inputterminal of the first comparison circuit 30 is coupled to the firstterminal of the resistor branch. After the current source circuit 10supplies the first mirror current signal to the resistor branch, avoltage is generated across the resistor branch. In a case where the lowlevel signal terminal VSS is grounded, a value of the voltage signalreceived by the non-inverting input terminal of the transconductanceamplifier OTA is the product of the resistance value of the resistorbranch and the first mirror current signal.

Further, as shown in FIG. 2, the first conversion sub-circuit 21includes a fourth resistor R4 and a fifth resistor R5. A first terminalof the fourth resistor R4 is coupled to a first terminal of the fifthresistor R5, a second terminal of the fourth resistor R4 is coupled tothe low level signal terminal VSS, and a second terminal of the fifthresistor R5 is coupled to the current source circuit 10.

Further, as shown in FIG. 2, the second conversion sub-circuit 22includes a third triode Q3, a base and a collector of the third triodeQ3 are both coupled to the low level signal terminal VSS, an emitter ofthe third triode Q3 is coupled to the second input terminal of the firstcomparison circuit 30 and the current source circuit 10, and abase-emitter voltage V_(BE3) of the third triode Q3 is negativelycorrelated with the temperature.

In practical applications, resistance values of the first resistor R1,the fourth resistor R4, and the fifth resistor R5 may be set as requiredsuch that the potential of the second terminal of the fifth resistor R5is lower than the potential of the emitter of the third triode Q3 whenthe temperature of the region where the control circuit is located iswithin a normal temperature range (e.g., lower than 60° C.), and thepotential of the second terminal of the fifth resistor R5 is higher thanthe potential of the emitter of the third triode Q3 when the temperatureof the region where the control circuit is located is higher than thenormal temperature range.

Further, as shown in FIGS. 1 and 2, the control circuit further includesa second comparison circuit 40 having a first input terminal, a secondinput terminal, and an output terminal. The first conversion sub-circuit21 is further configured to generate a third voltage signal positivelycorrelated with the current signal generated by the current sourcecircuit 10, and output the third voltage signal to the first inputterminal of the second comparison circuit 40. The third voltage signalis lower than the first voltage signal under the same current signal.The second conversion sub-circuit 22 is further configured to output thesecond voltage signal to the second input terminal of the secondcomparison circuit 40. The second comparison circuit 40 is configured tooutput a turn-off signal for controlling a display apparatus includingthe control circuit to be turned off when the voltage signal of thefirst input terminal of the second comparison circuit 40 is higher thanthe voltage signal of the second input terminal of the second comparisoncircuit 40.

For example, when the temperature of the display apparatus reaches afirst temperature (e.g., 60° C.), the first conversion sub-circuit 21generates a first voltage signal and a third voltage signal, and thesecond conversion sub-circuit 22 generates a second voltage signal, thefirst voltage signal is higher than the second voltage signal, and thethird voltage signal is lower than the second voltage signal. At thistime, the first comparison circuit 30 outputs a control signal tocontrol the brightness of the backlight. As the difference between thefirst voltage signal and the second voltage signal increases, thecontrol signal decreases, so that the brightness of the backlight islowered, thereby lowering the temperature of the display apparatus. Whenthe temperature of the display apparatus reaches a second temperature(e.g., 80° C.), the first voltage signal and the third voltage signalgenerated by the first conversion sub-circuit 21 are both higher thanthe second voltage signal generated by the second conversion sub-circuit22, so that the second comparison circuit 40 generates a turn-off signalto control the display apparatus to be turned off, thereby preventingthe display apparatus from being burned due to excessively hightemperature. It can be seen that the second comparison circuit 40 canachieve an over-temperature protection.

In some embodiments, the first input terminal of the second comparisoncircuit 40 is coupled to the first terminal of the fourth resistor R4.The second input terminal of the second comparison circuit 40 is coupledto the emitter of the third triode Q3. The second comparison circuit 40may include a voltage comparator CMP, a non-inverting input terminal ofthe voltage comparator CMP is coupled to the first input terminal of thesecond comparison circuit 40, and an inverting input terminal of thevoltage comparator CMP is coupled to the second input terminal of thesecond comparison circuit 40, and an output terminal of the voltagecomparator CMP is coupled to the output terminal of the secondcomparison circuit 40. In addition, in order to supply an operatingcurrent to the voltage comparator CMP, as shown in FIG. 2, the currentsource circuit 10 may further include an eighth P-type field effecttransistor PM8, a gate electrode of the eighth P-type field effecttransistor PM8 is coupled to the gate electrode of the first P-typefield effect transistor PM1, a first electrode of the eighth P-typefield effect transistor PM8 is coupled to the power supply terminal, anda second electrode of the eighth P-type field effect transistor PM8 iscoupled to a positive power supply terminal of the voltage comparatorCMP. A negative power supply terminal of the voltage comparator CMP iscoupled to the low level signal terminal VSS.

When the control circuit operates, the current generation circuit 11generates a bias current signal I_(BIAS) positively correlated with thetemperature, the first replica circuit 12 supplies the first mirrorcurrent signal I_(BIAS1) equal in magnitude to the bias current signalI_(BIAS) to the fourth resistor R4 and the fifth resistor R5, and thesecond replica circuit 13 supplies the second mirror current signalI_(BIAS2) equal in magnitude to the bias current signal to the thirdtriode Q3. When the temperature of the display apparatus is within anormal range (for example, below 60° C.), the I_(BIAS) is small, thevoltage at point A (i.e., the second terminal of the fifth resistor R5)is lower than the voltage at point C (i.e., the emitter of the thirdtriode Q3), and no current is input to the output terminal of thetransconductance amplifier OTA, I_(th)=0. As the temperature increases,the bias current signal I_(BIAS) gradually increases, and thebase-emitter voltage of the third triode Q3 gradually decreases. Whenthe temperature of the display apparatus rises to a first temperature(for example, 60° C.), the voltage at point A is higher than the voltageat point C, and a current flows into the transconductance amplifier OTA,I_(th)>0. That is, part of the current flowing in a branch in which thesixth resistor R6 and the seventh resistor R7 are located flows into thetransconductance amplifier OTA, so that the voltage across the sixthresistor R6 is reduced, and the control voltage V_(PWM) output by thefirst comparison circuit 30 is lowered. Moreover, as the temperatureincreases, I_(th) increases, the control signal V_(PWM) output by thefirst comparison circuit 30 decreases, so that the brightness of thebacklight is controlled to be lowered, thereby lowering the temperatureof the display apparatus. In a case where the temperature of the displayapparatus cannot be further lowered through the control signal V_(PWM),if the temperature of the display apparatus continues to rise to reach asecond temperature (for example, 80° C.), the bias current signalI_(BIAS) continues to rise, so that the voltage at point B (i.e., thefirst terminal of the fifth resistor) is also higher than the voltage atpoint C, and at this time, the second comparison circuit 40 outputs aturn-off signal V_(OTP) to control the display apparatus to be turnedoff.

As another aspect of the present disclosure, a light source drivingdevice including the above-described control circuit provided by thepresent disclosure and a light source driving circuit coupled to thecontrol circuit, the light source driving circuit is configured toadjust, according to the control signal output by the control circuit,the brightness of the light source such that the adjusted brightness ofthe light source is positively correlated with the magnitude of thecontrol signal. In an embodiment, the light source is a backlight.

In some embodiments, as shown in FIG. 3, the light source drivingcircuit includes a pulse generator 51, a power source 52, and a switchelement 53. The pulse generator 51 is coupled to the control circuit andconfigured to generate a pulse modulation signal according to thecontrol signal output by the control circuit, and a duty cycle of thepulse modulation signal is positively correlated with the magnitude ofthe control signal. The power source 52 is configured to supply acurrent to a light-emitting element 60 of the light source. The switchelement 53 is coupled to the pulse generator 51, the power source 52,and the light-emitting element 60, and is configured to controlconnection and disconnection between the power source 52 and thelight-emitting element 60 according to the pulse modulation signal tocontrol an average current of the light-emitting element.

In some embodiments, the switch element 53 is configured to be turned onupon receipt of a high level signal and be turned off upon receipt of alow level signal. The pulse generator 51 may include a voltagecomparison sub-circuit and an initial sawtooth wave signal generationsub-circuit, the initial sawtooth wave signal generation sub-circuitsupplies an initial sawtooth wave signal V1 to the second input terminalof the voltage comparison sub-circuit, and the control signal V_(PWM) isprovided to the first input terminal of the voltage comparisonsub-circuit. The voltage comparison sub-circuit is configured to outputa high level signal when the voltage of its first input terminal ishigher than the voltage of its second input terminal, and output a lowlevel signal when the voltage of its first input terminal is lower thanthe voltage of its second input terminal, thereby outputting the pulsemodulation signal.

The duty cycle of the pulse modulation signal is positively correlatedwith the magnitude of the control signal. The principle of obtaining thepulse modulation signal PWM from the sawtooth wave signal V1 and thecontrol signal V_(PWM) is as shown in FIG. 4.

As still another aspect of the present disclosure, there is provided adisplay apparatus including a display module and the above-describedlight source driving device, the display module includes a display paneland a backlight, the backlight is coupled to the light source drivingdevice, and the light source driving device is configured to adjustbrightness of the backlight.

As described above, the control circuit further includes a secondcomparison circuit. In this case, the display apparatus may furtherinclude a gating switch 70. As shown in FIG. 5, the gating switch 70 iscoupled to the output terminal of the second comparison circuit, a powersupply terminal VIN for supplying power to the display module LCM andthe display module LCM, and configured to disconnect the power supplyterminal from the display module LCM upon receipt of the turn-off signalfrom the second comparison circuit, so as to turn off the display moduleLCM.

The display apparatus may be any product or component having a displayfunction, such as a mobile phone, a tablet computer, a television, amonitor, a notebook computer, a digital photo frame, a navigator, or thelike.

In the light source driving device, the control circuit can generate acontrol signal having a magnitude negatively correlated with thetemperature, and the light source driving circuit can adjust brightnessof the backlight according to the control signal such that the adjustedbrightness of the backlight is positively correlated with the magnitudeof the control signal. Therefore, when the temperature rises, the lightsource driving device controls the brightness of the backlight to belowered, so as to lower the overall temperature of the displayapparatus, thereby ensuring normal operation of the display apparatus.When the temperature of the display apparatus is too high, the lightsource driving device can turn off the display apparatus to prevent thedisplay apparatus from being damaged due to the high temperature.

It could be understood that the above implementations are merelyexemplary implementations employed for explaining the principles of thepresent disclosure, but the present disclosure is not limited thereto.Various modifications and improvements can be made by those skilled inthe art without departing from the spirit and essence of the presentdisclosure, and these modifications and improvements are also consideredas falling within the protection scope of the present disclosure.

1. A control circuit comprising: a current source circuit, configured togenerate a current signal having a magnitude positively correlated witha temperature of a region where the control circuit is located; aconversion circuit, coupled to the current source circuit and configuredto convert the current signal generated by the current source circuitinto a voltage signal; and a first comparison circuit, coupled to theconversion circuit and configured to output a control signal forcontrolling brightness of a light source according to the voltage signalreceived from the conversion circuit, a magnitude of the control signalbeing negatively correlated with the temperature of the region where thecontrol circuit is located, and the brightness of the light source beingpositively correlated with the magnitude of the control signal.
 2. Thecontrol circuit of claim 1, wherein the first comparison circuitcomprises a first input terminal and a second input terminal, and atleast one of the first input terminal and the second input terminal iscoupled to the conversion circuit and configured to receive the voltagesignal from the conversion circuit, and the first comparison circuit isconfigured to output the control signal in response to a magnitude of avoltage signal input to the first input terminal being greater than amagnitude of a voltage signal input to the second input terminal, themagnitude of the control signal being negatively correlated with adifferent between the voltage signals input to the first input terminaland the second input terminal of the first comparison circuit.
 3. Thecontrol circuit of claim 2, wherein the conversion circuit comprises afirst conversion sub-circuit coupled to the first input terminal of thefirst comparison circuit and configured to provide a first voltagesignal to the first input terminal of the first comparison circuit, amagnitude of the first voltage signal being positively correlated with amagnitude of the current signal generated by the current source circuit.4. The control circuit of claim 3, wherein the conversion circuitcomprises a second conversion sub-circuit coupled to the second inputterminal of the first comparison circuit and configured to provide asecond voltage signal to the second input terminal of the firstcomparison circuit, a magnitude of the second voltage signal beingnegatively correlated with the magnitude of the current signal generatedby the current source circuit.
 5. The control circuit of claim 4,further comprising a second comparison circuit, wherein the secondcomparison circuit is configured to output a turn-off signal forcontrolling a display apparatus having the control circuit to be turnedoff in response to a magnitude of a voltage signal input to a firstinput terminal of the second comparison circuit being greater than amagnitude of a voltage signal input to a second input terminal of thesecond comparison circuit, and the first conversion sub-circuit isfurther coupled to the first input terminal of the second comparisoncircuit, and is configured to generate a third voltage signal having amagnitude positively correlated with the magnitude of the current signalgenerated by the current source circuit and output the third voltagesignal to the first input terminal of the second comparison circuit; themagnitude of the third voltage signal is smaller than the magnitude ofthe first voltage signal.
 6. The control circuit of claim 5, wherein thesecond conversion sub-circuit is further coupled to the second inputterminal of the second comparison circuit and configured to output thesecond voltage signal to the second input terminal of the secondcomparison circuit.
 7. The control circuit of claim 4, wherein thecurrent source circuit comprises a current generation circuit configuredto generate a bias current signal having a magnitude positivelycorrelated with the temperature of the region where the control circuitis located; the current source circuit further comprises a first replicacircuit coupled to the current generation circuit and the firstconversion sub-circuit, and configured to supply a first mirror currentsignal having a magnitude equal to the magnitude of the bias currentsignal and output the first mirror current signal to the firstconversion sub-circuit; and the first conversion sub-circuit isconfigured to convert the first mirror current signal into the firstvoltage signal.
 8. The control circuit of claim 7, wherein the currentsource circuit further comprises a second replica circuit coupled to thecurrent generation circuit and the second conversion sub-circuit, andconfigured to supply a second mirror current signal having a magnitudeequal to the magnitude of the bias current signal and output the secondmirror current signal to the second conversion sub-circuit; and thesecond conversion sub-circuit is configured to convert the second mirrorcurrent signal into the second voltage signal.
 9. The control circuit ofclaim 8, wherein the current generation circuit comprises a firsttriode, a second triode, a first resistor, a second resistor, a thirdresistor, a first P-type field effect transistor, a second P-type fieldeffect transistor, a third P-type field effect transistor, a fourthP-type field effect transistor, a first N-type field effect transistor,a second N-type field effect transistor, a third N-type field effecttransistor, and a fourth N-type field effect transistor; whereinwidth-to-length ratios of the first to fourth N-type field effecttransistors are the same, and width-to-length ratios of the first tofourth P-type field effect transistors are the same; a gate electrode ofthe first P-type field effect transistor is coupled to a secondelectrode of the second P-type field effect transistor, a firstelectrode of the first P-type field effect transistor is coupled to apower supply terminal, and a second electrode of the first P-type fieldeffect transistor is coupled to a first electrode of the second P-typefield effect transistor; a gate electrode of the third P-type fieldeffect transistor is coupled to the gate electrode of the first P-typefield effect transistor, a first electrode of the third P-type fieldeffect transistor is coupled to the power supply terminal, and a secondelectrode of the third P-type field effect transistor is coupled to afirst electrode of the fourth P-type field effect transistor; a gateelectrode of the fourth P-type field effect transistor is coupled to agate electrode of the second P-type field effect transistor and a firstelectrode of the third N-type field effect transistor, and a secondelectrode of the fourth P-type field effect transistor is coupled to agate electrode of the third N-type field effect transistor and a gateelectrode of the fourth N-type field effect transistor; a gate electrodeof the first N-type field effect transistor is coupled to a gateelectrode of the second N-type field effect transistor and a firstelectrode of the fourth N-type field effect transistor, and a firstelectrode of the first N-type field effect transistor is coupled to asecond electrode of the third N-type field effect transistor; a firstelectrode of the second N-type field effect transistor is coupled to asecond electrode of the fourth N-type field effect transistor; a firstterminal of the first resistor is coupled to a second electrode of thefirst N-type field effect transistor, a second terminal of the firstresistor is coupled to an emitter of the first triode, an emitter of thesecond triode is coupled to a second electrode of the second N-typefield effect transistor, and a base and a collector of the first triodeand a base and a collector of the second triode are all coupled to a lowlevel signal terminal; a first terminal of the second resistor iscoupled to the second electrode of the second P-type field effecttransistor, and a second terminal of the second resistor is coupled tothe first electrode of the third N-type field effect transistor; and afirst terminal of the third resistor is coupled to the second electrodeof the fourth P-type field effect transistor, and a second terminal ofthe third resistor is coupled to the first electrode of the fourthN-type field effect transistor.
 10. The control circuit of claim 9,wherein the first replica circuit comprises a fifth P-type field effecttransistor, a gate electrode of the fifth P-type field effect transistoris coupled to the gate electrode of the first P-type field effecttransistor, a first electrode of the fifth P-type field effecttransistor is coupled to the power supply terminal, and a secondelectrode of the fifth P-type field effect transistor is coupled to thefirst conversion sub-circuit; and a width-to-length ratio of the fifthP-type field effect transistor is equal to the width-to-length ratio ofthe first P-type field effect transistor.
 11. The control circuit ofclaim 10, wherein the second replica circuit comprises a sixth P-typefield effect transistor, a gate electrode of the sixth P-type fieldeffect transistor is coupled to the gate electrode of the first P-typefield effect transistor, a first electrode of the sixth P-type fieldeffect transistor is coupled to the power supply terminal, and a secondelectrode of the sixth P-type field effect transistor is coupled to thesecond conversion sub-circuit; and a width-to-length ratio of the sixthP-type field effect transistor is equal to the width-to-length ratio ofthe first P-type field effect transistor.
 12. The control circuit ofclaim 11, wherein the first comparison circuit comprises: atransconductance amplifier having a non-inverting input terminal coupledto the first input terminal of the first comparison circuit, aninverting input terminal coupled to the second input terminal of thefirst comparison circuit, and an output terminal coupled to an outputterminal of the first comparison circuit; a sixth resistor having afirst terminal coupled to the output terminal of the first comparisoncircuit and a second terminal coupled to the low level signal terminal;and a seventh resistor having a first terminal coupled to the powersupply terminal, and a second terminal coupled to the output terminal ofthe first comparison circuit.
 13. The control circuit of claim 12,wherein the first conversion sub-circuit comprises a resistor branchcomprising at least one resistor, a first terminal of the resistorbranch is coupled to the second electrode of the fifth P-type fieldeffect transistor, a second terminal of the resistor branch is coupledto the low level signal terminal, and the first input terminal of thefirst comparison circuit is coupled to the first terminal of theresistor branch.
 14. The control circuit of claim 12, wherein the secondconversion sub-circuit comprises a third triode, a base and a collectorof the third triode are coupled to the low level signal terminal, and anemitter of the third triode is coupled to the second input terminal ofthe first comparison circuit and the second electrode of the sixthP-type field effect transistor.
 15. The control circuit of claim 14,wherein the first conversion sub-circuit comprises a fourth resistor anda fifth resistor, a first terminal of the fourth resistor is coupled toa first terminal of the fifth resistor, a second terminal of the fourthresistor is coupled to the low level signal terminal, and a secondterminal of the fifth resistor is coupled to the second electrode of thefifth P-type field effect transistor; and the first input terminal ofthe second comparison circuit is coupled to the first terminal of thefourth resistor, and the second input terminal of the second comparisoncircuit is coupled to the emitter of the third triode.
 16. The controlcircuit of claim 6, wherein the second comparison circuit comprises avoltage comparator, a non-inverting input terminal of the voltagecomparator is coupled to the first input terminal of the secondcomparison circuit, an inverting input terminal of the voltagecomparator is coupled to the second input terminal of the secondcomparison circuit, and an output terminal of the voltage comparator iscoupled to the output terminal of the second comparison circuit.
 17. Alight source driving device, comprising the control circuit of claim 1and a light source driving circuit coupled to the control circuit,wherein the light source driving circuit is configured to adjust thebrightness of the light source according to the control signal output bythe control circuit such that the adjusted brightness of the lightsource is positively correlated with the magnitude of the controlsignal.
 18. The light source driving device of claim 17, wherein thelight source driving circuit comprises: a pulse generator coupled to thecontrol circuit and configured to generate a pulse modulation signalaccording to the control signal output by the control circuit, a dutycycle of the pulse modulation signal being positively correlated withthe magnitude of the control signal; a power source configured toprovide a current to a light-emitting element of the light source; and aswitch element coupled to the pulse generator, the power source, and thelight-emitting element, and configured to control connection anddisconnection between the power source and the light-emitting elementaccording to the pulse modulation signal from the pulse generator tocontrol an average current of the light-emitting element.
 19. A displayapparatus, comprising a display module and the light source drivingdevice of claim 17, wherein the display module comprises a backlightcoupled to the light source driving device, and the light source drivingdevice is configured to adjust brightness of the backlight.
 20. Thedisplay apparatus of claim 19, further comprising a gating switch,wherein the control circuit in the light source driving device furthercomprises a second comparison circuit configured to output a turn-offsignal in response to a magnitude of a voltage signal input to a firstinput terminal of the second comparison circuit being greater than amagnitude of a voltage signal input to a second input terminal of thesecond comparison circuit, the gating switch is coupled between thedisplay module and a power supply terminal for supplying power to thedisplay module, a control terminal of the gating switch is coupled tothe second comparison circuit of the control circuit, and the gatingswitch is configured to disconnect the power supply terminal from thedisplay module upon receipt of the turn-off signal from the secondcomparison circuit of the control circuit.